Water from seas, inlets, rivers, lakes and other bodies of water can be used in a variety of different ways, for example, as coolant in power plant operation. Some thermal and nuclear power plants are located near bodies of water which shelter large numbers of fish or which serve as breeding and nursery grounds for fish. When small fish hibernate or when fish spend their juvenile period in these bodies of water and when these bodies of water are used to supply cooling water to nearby power plants, fish in the water are easily sucked or pulled into the cooling water intake pipes of the power plants. This situation produces problems, e.g. the clogging of the screens of the cooling water intakes of the power plant and death of the fish.
To prevent screen clogging and/or fish kill, various techniques and screens have been proposed or used to prevent the fish from entering the cooling water intake conduit of a power plant. It appears that a screen alone or a screen provided with a backwash device is not sufficient. When fish are immature or wintering, they cannot avoid the pull or suction of the intake conduits and become caught on the intake conduit screen, not only resulting in a clogged screen and preventing water from entering the power plant but also resulting in the fish being killed due to entrapment on the screen. A jet of water directed against the screen only momentarily releases the fish from the screen since the suction of the water flowing through the screen into the supply conduit again siezes the fish and returns them to the screen.
A water intake device in accordance with this invention comprises a movable screen, such as a substantially cylindrical rotatable screen, adapted to be at least partially submerged in a body of water. A water supply conduit communicates with the interior of the screen to receive the water flowing therethrough. Backwashing means associated with the screen, such as means to project jets of water, direct water jets at a section or segment of the screen as that section or segment moves the backwashing means. The jets of water serve to clear and/or remove objects or fish caught on the outside of the screen. Duct means are also provided associated with the screen and the backwashing means to provide a flow channel for the objects or fish removed from the screen by the backwashing means. The duct means are dimensioned and positioned so as to carry objects or fish removed from the screen beyond the pull or suction of the water entering the screen.
Other water intake devices or water filtering devices are disclosed in U.S. Pat. Nos. 630,769, 682,994, 788,511, 1,109,385, 1,516,693, 2,022,336, 2,223,104, 2,901,113, 3,333,700, 3,349,916 and 3,843,520. The disclosures of these patents are herein incorporated and made part of this disclosure. However, the prior art and none of these patents discloses the subject invention, i.e. a movable screen provided with backwashing means and duct means associated therewith to remove backwashed material or fish from the pull of or suction of the water entering the screen to the water supply conduit.
It is an object of this invention to provide a water intake device for supplying water for use in the operation of power plants and other installations which require a large volume of water.
It is also an object of this invention to provide a water intake device provided with a screen wherein the screen is continuously cleaned and objects and fish cleared therefrom will not immediately be returned to the screen but are directed away from the screen.